U.S. patent application number 13/365506 was filed with the patent office on 2012-08-09 for electromagnetic valve.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Yuichiro MIURA.
Application Number | 20120199773 13/365506 |
Document ID | / |
Family ID | 46600036 |
Filed Date | 2012-08-09 |
United States Patent
Application |
20120199773 |
Kind Code |
A1 |
MIURA; Yuichiro |
August 9, 2012 |
ELECTROMAGNETIC VALVE
Abstract
An electromagnetic valve includes a valve seat, a valving
element, and a solenoid part. The valve seat has an annular shape
and defines a valve hole. The solenoid part includes a coil, a core
guide part, a fixed core, and a movable core. The coil becomes an
electromagnet upon energization thereof. The core guide part is
arranged radially inward of the coil. The movable core is
accommodated and reciprocated inside the core guide part in
accordance with whether the electromagnet is turned on or off. The
valving element moves integrally with the movable core to open or
close the valve hole. The core guide part includes a magnetic
unbalance part where magnetic force applied between the core guide
part and the movable core is different between on one side and the
other side of the core guide part in its radial direction.
Inventors: |
MIURA; Yuichiro; (Obu-city,
JP) |
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
46600036 |
Appl. No.: |
13/365506 |
Filed: |
February 3, 2012 |
Current U.S.
Class: |
251/129.15 |
Current CPC
Class: |
F16K 31/06 20130101;
H01F 2007/085 20130101; F16K 31/0675 20130101; F16K 31/0658
20130101 |
Class at
Publication: |
251/129.15 |
International
Class: |
F16K 31/02 20060101
F16K031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2011 |
JP |
2011-22509 |
Claims
1. An electromagnetic valve comprising: a valve seat having an
annular shape and defining a valve hole that opens radially inward
of the valve seat; a valving element provided to be movable between
a valve-closing position where the valving element is engaged with
the valve seat to close the valve hole and a valve-opening position
where the valving element is disengaged from the valve seat to open
the valve hole; and a solenoid part configured to drive the valving
element by utilizing magnetic force of an electromagnet, wherein:
the solenoid part includes: a coil which becomes the electromagnet
upon energization thereof; a core guide part which has a
cylindrical shape and is arranged radially inward of the coil to
form a magnetic circuit; a fixed core which is arranged on one end
side of the core guide part in an axial direction of the core guide
part and is magnetized by the electromagnet; and a movable core
which is accommodated inside the core guide part to be opposed to
the fixed core in the axial direction and which is reciprocated
inside the core guide part in accordance with whether the
electromagnet is turned on or off; the valving element moves
integrally with the movable core to open or close the valve hole;
and the core guide part includes a magnetic unbalance part where
the magnetic force applied between the core guide part and the
movable core is different between on one side and the other side of
the core guide part, which are opposed to each other in a radial
direction of the core guide part.
2. The electromagnetic valve according to claim 1, wherein: the
core guide part includes a magnetic saturation part along an entire
outer circumference thereof; the magnetic saturation part includes
a recessed part on an outer peripheral surface thereof, to reduce a
thickness of the core guide part, thereby decreasing a
magnetic-path cross-sectional area of the magnetic saturation part;
and at the magnetic unbalance part, the magnetic-path
cross-sectional area of the magnetic saturation part is different
between on the one side and the other side of the core guide
part.
3. The electromagnetic valve according to claim 2, wherein an outer
diameter center of the magnetic saturation part is positioned
eccentrically with respect to a diameter center of the core guide
part.
4. The electromagnetic valve according to claim 2, wherein: an
outer diameter center of the magnetic saturation part coincides
with an outer diameter center of the core guide part; and a
diameter center of an inner peripheral surface of the core guide
part, which accommodates the movable core, is located eccentrically
with respect to the outer diameter center of the core guide
part.
5. The electromagnetic valve according to claim 1, wherein at the
magnetic unbalance part, the core guide part includes a through
hole, which passes through a circumferential wall of the core guide
part, only on the one side or the other side of the core guide
part.
6. The electromagnetic valve according to claim 5, wherein: the
core guide part includes a magnetic saturation part along an entire
outer circumference thereof; the magnetic saturation part includes
a recessed part on an outer peripheral surface thereof, to reduce a
thickness of the core guide part, thereby decreasing a
magnetic-path cross-sectional area of the magnetic saturation part;
and the through hole is provided at the magnetic saturation
part.
7. The electromagnetic valve according to claim 1, wherein: at the
magnetic unbalance part, each of the one side and the other side of
the core guide part includes at least one through hole, which
passes through a circumferential wall of the core guide part; and a
number of the at least one through hole on the one side of the core
guide part is different from a number of the at least one through
hole on the other side of the core guide part.
8. The electromagnetic valve according to claim 7, wherein: the
core guide part includes a magnetic saturation part along an entire
outer circumference thereof; the magnetic saturation part includes
a recessed part on an outer peripheral surface thereof, to reduce a
thickness of the core guide part, thereby decreasing a
magnetic-path cross-sectional area of the magnetic saturation part;
and the at least one through hole on the one side of the core guide
part and the at least one through hole on the other side of the
core guide part are provided at the magnetic saturation part.
9. The electromagnetic valve according to claim 1, wherein: at the
magnetic unbalance part, each of the one side and the other side of
the core guide part includes a through hole, which passes through a
circumferential wall of the core guide part; and a diameter of the
through hole on the one side of the core guide part and a diameter
of the through hole on the other side of the core guide part are
different from each other.
10. The electromagnetic valve according to claim 9, wherein: the
core guide part includes a magnetic saturation part along an entire
outer circumference thereof; the magnetic saturation part includes
a recessed part on an outer peripheral surface thereof, to reduce a
thickness of the core guide part, thereby decreasing a
magnetic-path cross-sectional area of the magnetic saturation part;
and the through hole on the one side of the core guide part and the
through hole on the other side of the core guide part are provided
at the magnetic saturation part.
11. The electromagnetic valve according to claim 1, wherein only a
part of an outer peripheral surface of the movable core, which
slides on an inner peripheral surface of the core guide part, is
coated with a coating agent.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2011-022509 filed on Feb.
4, 2011.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electromagnetic valve
whose valving element is actuated by utilizing magnetic force of an
electromagnet.
[0004] 2. Description of Related Art
[0005] An example of a conventional normally-closed electromagnetic
valve will be described. In the normally-closed electromagnetic
valve, an electromagnet is produced by energization of a coil. A
movable core is attracted to and contacts with a fixed core
magnetized by the electromagnet, so that a valving element attached
to the movable core is disengaged from a valve seat to cause the
electromagnetic valve to be open. When the energization of the coil
is stopped and magnetic force of the electromagnet disappears, the
movable core is pushed back in an opposite direction from the fixed
core by reactive force of a return spring, and the valving element
is engaged with the valve seat, thereby to close the
electromagnetic valve. In the above-described electromagnetic
valve, for example, an elastic body such as rubber can be used for
the valving element. In this case, by the repeated opening and
closing operation of the valving element for a long period, plastic
deformations such as wear and creep are produced in the valving
element and the valve seat, so that the valving element and the
valve seat are shaped to conform to each other. Thus, a sealing
performance when the valving element sits on the valve seat is
improved as time passes. However, if the movable core, to which the
valving element is attached, rotates while the movable core is
attracted and moves to the fixed core, the above-described portions
of the valving element and the valve seat, which are conformed in
form with each other, are relatively shifted from each other.
Therefore, the sealing performance when the valving element sits on
the valve seat cannot be maintained.
[0006] For the measures against this problem, a technology (see,
JP2005-214225A, JP2005-98340A) is known. According to this
technology, the movable core is attracted on radially one side of a
cylindrical core guide part for guiding the movable core when the
movable core is attracted and moves to the fixed core. In
JP2005-214225A, the center of the return spring which urges the
movable core is eccentrically arranged relative to the central axis
of the movable core, so that the movable core is pressed against
one side of the core guide part and rotation of the movable core is
limited. In JP2005-98340A, a gap expansion part, which expands a
gap between the movable core and the core guide part, is formed on
an outer periphery of the movable core, or an attachment center of
an impact absorbing means, which is attached to the movable core,
is made eccentric from the center of the movable core. As a result,
the movable core is pushed against one side of the core guide part,
and rotation of the movable core is prevented.
[0007] However, in JP2005-214225A, because an action center of
urging force of the return spring applied to the movable core is
shifted from the center line of the movable core, a sealing load
may be one-sided when the valving element sits on the valve seat,
and leakage from the electromagnetic valve may occur. In
JP2005-98340A, a gravity center of the movable core is shifted from
the center line of the movable core, i.e., the gravity center is
not located on the same line as the center line of the movable
core. Therefore, in the electromagnetic valve disposed in a
vehicle, for example, rotation of the movable core may be not
limited due to its install direction, an acceleration of the
vehicle, a centrifugal force and so on.
SUMMARY OF THE INVENTION
[0008] The present invention addresses at least one of the above
disadvantages.
[0009] According to the present invention, there is provided an
electromagnetic valve including a valve seat, a valving element,
and a solenoid part. The valve seat has an annular shape and
defines a valve hole that opens radially inward of the valve seat.
The valving element is provided to be movable between a
valve-closing position where the valving element is engaged with
the valve seat to close the valve hole and a valve-opening position
where the valving element is disengaged from the valve seat to open
the valve hole. The solenoid part is configured to drive the
valving element by utilizing magnetic force of an electromagnet.
The solenoid part includes a coil, a core guide part, a fixed core,
and a movable core. The coil becomes the electromagnet upon
energization thereof. The core guide part has a cylindrical shape
and is arranged radially inward of the coil to form a magnetic
circuit. The fixed core is arranged on one end side of the core
guide part in an axial direction of the core guide part and is
magnetized by the electromagnet. The movable core is accommodated
inside the core guide part to be opposed to the fixed core in the
axial direction and is reciprocated inside the core guide part in
accordance with whether the electromagnet is turned on or off. The
valving element moves integrally with the movable core to open or
close the valve hole. The core guide part includes a magnetic
unbalance part where the magnetic force applied between the core
guide part and the movable core is different between on one side
and the other side of the core guide part, which are opposed to
each other in a radial direction of the core guide part.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0011] FIG. 1 is a sectional view illustrating a solenoid part
according to a first embodiment of the invention;
[0012] FIG. 2 is a sectional view of the solenoid part illustrating
unbalance magnetic force applied between a core guide part and a
movable core according to the first embodiment;
[0013] FIG. 3A is a sectional view illustrating the solenoid part
excluding the movable core according to the first embodiment;
[0014] FIG. 3B is a cross-sectional view taken along a line
IIIB-IIIB of FIG. 3A and illustrating a magnetic saturation part
provided in the core guide part;
[0015] FIG. 4 is a schematic diagram illustrating a fuel vapor
treatment system according to the first embodiment;
[0016] FIG. 5A is a sectional view illustrating a solenoid part
excluding a movable core according to a second embodiment of the
invention;
[0017] FIG. 5B is a cross-sectional view taken along a line VB-VB
of FIG. 5A and illustrating a magnetic saturation part provided in
a core guide part;
[0018] FIG. 6A is a sectional view illustrating a solenoid part
excluding a movable core according to a third embodiment of the
invention;
[0019] FIG. 6B is a cross-sectional view taken along a line VIB-VIB
of FIG. 6A and illustrating a magnetic saturation part provided in
a core guide part;
[0020] FIG. 7A is a sectional view illustrating a solenoid part
excluding a movable core according to a fourth embodiment of the
invention;
[0021] FIG. 7B is a cross-sectional view taken along a line
VIIB-VIIB of FIG. 7A and illustrating a magnetic saturation part
provided in a core guide part; and
[0022] FIG. 8 is a perspective view illustrating a movable core
according to a fifth embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Modes of the invention will be in detail described based on
embodiments below.
First Embodiment
[0024] In a first embodiment, an electromagnetic valve of the
invention is applied to a fuel vapor treatment system of a vehicle.
As shown in FIG. 4, the fuel vapor treatment system prevents fuel
vapor from emitting into the atmosphere. Fuel vapor is evaporated
inside a fuel tank 1 disposed in the vehicle, The fuel vapor
treatment system includes a canister 2 which temporarily adsorbs
and holds fuel vapor leaked from the tank 1. The canister 2 is
filled with an adsorption agent such as an activated carbon, which
adsorbs fuel vapor. The canister 2 includes a vapor port 2a, a
purge port 2b, and an air port 2c. The vapor port 2a is connected
to the tank 1 through a vapor passage 3, and the purge port 2b is
connected to an intake pipe 5 of an internal combustion engine
through a purge passage 4. The air port 2c opens to the atmosphere
through an air passage 6.
[0025] A purge valve 7 is provided along the purge passage 4. The
purge valve 7 regulates a flow volume of fuel vapor, which is
suctioned into the intake pipe 5 from the canister 2 by intake
negative pressure in the internal combustion engine. The
electromagnetic valve of the invention is applied to the purge
valve 7. A throttle valve 8 is provided in the intake pipe 5. The
purge passage 4 is connected to the intake pipe 5 on a downstream
side (internal combustion engine-side) of the throttle valve 8 in
an intake-air flow direction. In the air passage 6, a filter 9 and
a normally-open canister control valve 10 are provided. The filter
9 filtrates air flowing into the canister 2, and the canister
control valve 10 causes the air port 2c of the canister 2 to be
closed as necessary. The filter 9 can be incorporated into the
purge valve 7, and, in this case, the filter 9 provided in the air
passage 6 may be omitted.
[0026] A structure of the purge valve 7 of the invention will be
described referring to FIG. 1. The purge valve 7 includes a housing
(not shown), a valving element 11, and a solenoid part 12. The
housing defines a connection passage communicating with the purge
passage 4. The valving element 11 is accommodated inside the
housing, and the solenoid part 12 actuates the valving element 11
by utilizing magnetic force of an electromagnet. The connection
passage of the housing includes an inflow port, an outflow port,
and a communication passage. The inflow port is connected to the
purge passage 4 on an upstream side (canister 2-side) of the purge
valve 7 in a flow direction of fuel vapor, and the outflow port is
connected to the purge passage 4 on a downstream side (intake pipe
5-side) of the purge valve 7 in the flow direction of fuel vapor.
The inflow port and the outflow port communicate with each other
through the communication passage. An annular valve seat 13 is
provided in the communication passage. The valving element 11 is
made of, for example, rubber elastic body (e.g., fluorine-contained
rubber, silicon rubber) and can cause a valve hole 14 to be opened
and closed. The valve hole 14 opens radially inward of the valve
seat 13. When the valving element 11 is engaged with the valve seat
13 to close the valve hole 14, a communication between the inflow
port and the outflow port is closed. When the valving element 11 is
disengaged from the valve seat 13 to open the valve hole 14, the
communication between the inflow port and the outflow port is
made.
[0027] The solenoid part 12 includes a coil 15, a magnetic-circuit
forming member, a movable core 16, and a coil spring 17. The coil
15 is wound around a bobbin (not shown) having an insulation
property, and the magnetic-circuit forming member forms a magnetic
circuit around the coil 15. The movable core 16 moves in an axial
direction of the coil 15 (in a vertical direction in FIG. 1), and
the coil spring 17 urges the movable core 16 in one direction. The
coil 15 is energized and controlled by an engine control unit (ECU)
via a drive circuit (not shown) and becomes an electromagnet as a
result of the supply of an excitation current. The magnetic-circuit
forming member includes a yoke 18, a core guide part 19, and a
fixed core 20. The yoke 18 is a part of the magnetic circuit
located on an outer periphery of the coil 15. The core guide part
19 is a part of the magnetic circuit located on an inner periphery
of the coil 15. The fixed core 20 is located on one side of the
core guide part 19 in the axial direction of the coil 15. The yoke
18 includes an outer-periphery yoke part and a bottom yoke part.
The outer-periphery yoke part covers the outer periphery of the
coil 15 along an entire length of the coil 15 in the axial
direction of the coil 15. The bottom yoke part covers an end
surface of the coil 15 on the one side of the coil 15 in the axial
direction.
[0028] The core guide part 19 has a cylindrical shape coaxially
with the coil 15 and defines a guide hole 19a (see FIG. 3A) in
which the movable core 16 is contained. An inner surface of the
guide hole 19a is a cylindrical surface which has a constant inner
diameter entirely in its longitudinal direction. A core plate 19b
is integrally formed with the core guide part 19 on an opposite
side from the fixed core 20 (on the other side of the core guide
part 19) in the axial direction. The core plate 19b extends
radially outward from the core guide part 19 to have a flange-like
shape. The core plate 19b covers an end surface of the coil 15 on
the other side of the coil 15 in the axial direction and is a part
of the magnetic circuit which is connected to the yoke 18. In the
core guide part 19, a magnetic saturation part 21 and a magnetic
unbalance part 24 are provided. The fixed core 20 serves as an
attraction part, which attracts the movable core 16 in the axial
direction due to magnetization of the fixed core 20 by energization
of the coil 15. As shown in FIG. 1, the fixed core 20 is integrally
provided with the core guide part 19, but these two can be
separately provided from each other.
[0029] The movable core 16 is contained in the guide hole 19a
defined by the core guide part 19, and moves in the guide hole 19a
in the axial direction (vertical direction in FIG. 1) of the core
guide part 19, facing to the fixed core 20. The movable core 16
having a cylindrical shape defines a spring chamber 16a inside an
inner periphery of the movable core 16. An opening of the movable
core 16 on an opposite side thereof from the fixed core 20 is
closed by an end board 16b, to which the valving element 11 is
attached. An outer circumferential surface of the movable core 16
is a cylindrical surface which has a constant outer diameter
entirely in its longitudinal direction. The outer diameter is
slightly smaller than the inner diameter of the guide hole 19a, so
that the movable core 16 can be reciprocated in the axial direction
of the core guide part 19 in the guide hole 19a. The coil spring 17
is accommodated in the spring chamber 16a of the movable core 16
and located coaxially with the movable core 16. An end part of the
coil spring 17 on its one end side in an axial direction thereof is
supported by an end surface of the fixed core 20, and an end part
of the coil spring 17 on its other end side in the axial direction
thereof is supported by the end board 16b of the movable core 16.
Thus, the coil spring 17 urges the movable core 16 in an opposite
direction from the fixed core 20 (in an upper direction in FIG. 1),
i.e., in a closing direction in which the valving element 11 is
engaged with the valve seat 13 to close the valve hole 14.
[0030] The magnetic saturation part 21 and the magnetic unbalance
part 24, which are provided in the core guide part 19, will be
described referring to FIGS. 3A and 3B. As shown in FIG. 3A, the
magnetic saturation part 21 is provided in the core guide part 19
by forming a recessed part on an entire outer circumference of the
core guide part 19 in vicinity to the fixed core 20 to reduce a
thickness of the core guide part 19. Thus, the magnetic saturation
part 21, where magnetic resistance is enhanced by the reduction of
a cross-sectional area (thickness) of the magnetic circuit (core
guide part 19), is provided in an entire circumference of the core
guide part 19. By forming the magnetic saturation part 21 in the
core guide part 19, a magnetic flux flowing directly from the core
guide part 19 to the fixed core 20 decreases. Hence, a magnetic
force applied between the core guide part 19 and the movable core
16 increases by the decrease of the magnetic flux. Therefore, an
attraction force acting between the core guide part 19 and the
movable core 16 increases.
[0031] The magnetic unbalance part 24 is provided such that the
magnetic circuit area of the magnetic saturation part 21 provided
in the core guide part 19, i.e., the cross-sectional area of the
thickness-reduced part of the core guide part 19 is different
between on one side and the other side of the core guide part 19,
which are opposed to each other in the radial direction of the core
guide part 19. That is, magnetic forces, which act between the core
guide part 19 and the movable core 16, on the one side and on the
other side of the core guide part 19 in the radial direction are
different from each other. Specifically, as shown in FIG. 3B, the
unbalance part 24 is provided at a position where the outer
diameter center Oa of the core guide part 19 (an inner diameter
center of the guide hole 19a) is eccentrically located relative to
an outer diameter center Ob of the magnetic saturation part 21. As
indicated by an arrow in FIG. 3A, the magnetic saturation part 21
is leaned to the other side (right side in FIG. 3A) of the core
guide part 19 as a whole in the radial direction of the core guide
part 19. The cross-sectional area of the magnetic saturation part
21 as the magnetic circuit is not constant along the entire
circumference of the core guide part 19, thereby being smaller on a
left side than on a right side of the core guide part 19 in FIG.
3B.
[0032] Magnetic forces, which act between the core guide part 19
and the movable core 16, are different between on the one side and
the other side of the core guide part 19, which are opposed to one
another in the radial direction. In the present embodiment, the one
side of the core guide part 19 has a smaller magnetic circuit area
than the other side thereof in the radial direction. Hence, the
magnetic force on the one side of the core guide part 19 more
strongly acts between the core guide part 19 and the movable core
16 than on the other side of the core guide part 19 in the radial
direction. Thus, the movable core 16 is attracted to the one side
of the core guide part 19 in the guide hole 19a. As described
above, the magnetic saturation part 21 is leaned entirely to the
other side of the core guide part 19 in the radial direction.
Therefore, as shown in FIG. 3B, the cross-sectional area of the
magnetic saturation part 21 as the magnetic circuit (the
cross-sectional area of the thickness-reduced part) gradually
change in a circumferential direction of the core guide part 19
without drastically changing between the smallest area part and the
largest area part of the magnetic saturation part 21.
[0033] An operation and effect of the purge valve 7 of the first
embodiment will be described. The magnetic unbalance part 24 is
provided in the core guide part 19, which is provided in the
solenoid part 12 of the purge valve 7 of the present embodiment.
More specifically, the cross-sectional magnetic circuit area of the
magnetic saturation part 21 (the cross-sectional area of the
thickness-reduced part) is smaller on the one side than on the
other side of the core guide part 19 which is opposed to the one
side in the radial direction. The saturation part 21 functions as
the magnetic circuit and is provided for the entire circumference
of the core guide part 19. Consequently, magnetic resistance in the
magnetic saturation part 21 becomes large on the one side of the
core guide part 19, which has a smaller cross-sectional area of the
magnetic circuit than the other side of the core guide part 19.
Therefore, as indicated in thickness of arrows in FIG. 2, the
magnetic force, which acts between the core guide part 19 and the
movable core 16, on the one side of the core guide part 19 becomes
large relative to the magnetic force on the other side of the core
guide part 19.
[0034] When the movable core 16 is attracted to the fixed core 20
magnetized by energization of the coil 15, i.e., when the movable
core 16 moves in the guide hole 19a in the axial direction of the
core guide part 19, the movable core 16 is attracted to and
contacts with the one side of the core guide part 19 in the radial
direction, where magnetic force more strongly acts on the movable
core 16. Accordingly, rotation of the movable core 16 is prevented.
Because the unbalance part 24 is not provided in the movable core
16, a gravity center of the movable core 16 is not shifted from a
radial center thereof. Therefore, because the gravity center of the
movable core 16 is located at the radial center thereof, rotation
of the movable core 16 due to, for example, its install direction
with respect to the vehicle, an acceleration of the vehicle, or a
centrifugal force does not occur.
[0035] The valving element 11 attached to the end board 16b of the
movable core 16 is always engaged with the same position of the
valve seat 13 at closing time when the valve hole 14 is closed.
Hence, as a result of the repeated opening and closing operation of
the valving element 11, the valving element 11 and the valve seat
13 are shaped to conform with each other, and sealing performance
at the closing time is improved. The movable core 16 is attracted
to and contacts with the one side of the core guide part 19 in the
radial direction when the movable core 16 moves in the guide hole
19a. Thus, sliding resistance is produced between the movable core
16 and the core guide part 19, and travel speed of the movable core
16 thereby becomes slow. As a result, an impact noise, which is
produced when the movable core 16 contacts with the fixed core 20,
is reduced.
Second Embodiment
[0036] As shown in FIGS. 5A and 5B, a second embodiment is an
example in which a magnetic unbalance part 24 is provided by
positioning an inner diameter center Oc of a guide hole 19a
eccentrically relative to an outer diameter center Oa of a core
guide part 19. A magnetic saturation part 21 is provided in the
core guide part 19 such that a recessed part is formed on an outer
peripheral surface of the core guide part 19, and a depth of the
recessed part is constant along the entire circumference of the
core guide part 19. That is, the outer diameter center Oa of the
core guide part 19 is located at the same position as a position of
an outer diameter center Ob of the magnetic saturation part 21. As
shown in FIG. 5B, the inner diameter center Oc of the guide hole
19a defined by the core guide part 19 is eccentrically positioned
on one side (left side in FIG. 5A) of the core guide part 19 in a
radial direction of the core guide part 19 with respect to the
outer diameter center Oa of the core guide part 19. Therefore, the
entire portion of the guide hole 19a is formed unevenly on the one
side of the core guide part 19 in the radial direction.
[0037] A magnetic-path cross-sectional area of the magnetic
saturation part 21 (a cross-sectional area of a thickness-reduced
part) is smaller on the one side than on the other side of the core
guide part 19, which is opposed to the one side in the radial
direction. The magnetic saturation part 21 functions as a magnetic
circuit and is formed along an entire circumference of the core
guide part 19. Consequently, similar to the first embodiment,
magnetic resistance in the magnetic saturation part 21 is large on
the one side of the core guide part 19, which has a smaller
cross-sectional area of the magnetic circuit than the other side of
the core guide part 19. Therefore, a magnetic force, which acts
between the core guide part 19 and the movable core 16, on the one
side of the core guide part 19 is large relative to a magnetic
force on the other side of the core guide part 19. When the movable
core 16 moves in the guide hole 19a in an axial direction of the
core guide part 19, the movable core 16 is attracted to and
contacts with the one side of the core guide part 19 in the radial
direction, where magnetic force more strongly acts on the movable
core 16. Thus, rotation of the movable core 16 is prevented.
Accordingly, similar effects (e.g., improvement of sealing
performance at valve closing time, and noise abatement) to the
first embodiment can be obtained.
Third Embodiment
[0038] As shown in FIGS. 6A and 6B, a third embodiment is an
example in which a magnetic unbalance part 24 is provided by boring
a through hole 22 on a circumferential wall of a core guide part
19. If the through hole 22 is bored on the circumferential wall of
the core guide part 19 including a magnetic saturation part 21, a
cross-sectional area of the magnetic saturation part 21 as a
magnetic circuit is further reduced and magnetic resistance
increases. As shown in FIG. 6B, if several through holes 22 are
provided only for one side (left side in FIG. 6A) of the core guide
part 19 in a radial direction of the core guide part 19, magnetic
resistance on the one side of the magnetic saturation part 21 in
the radial direction becomes large relative to magnetic resistance
on the other side of the magnetic saturation part 21, which is
opposed to the one side in the radial direction. Thus, when a
movable core 16 moves in the guide hole 19a in an axial direction
of the core guide part 19, the movable core 16 is attracted to and
contacts with the one side of the core guide part 19 in the radial
direction, where magnetic force more strongly acts on the movable
core 16. Accordingly, rotation of the movable core 16 is prevented.
The through hole 22 can be formed by laser radiation, cutting,
water jet cutting, or press working, for example. In FIGS. 6A and
6B, several through holes 22 are provided only for the one side of
the core guide part 19, which is opposed to the other side in the
radial direction. However, a magnetic unbalance part 24 can be
provided such that through holes 22 are provided also on the other
side of the core guide part 19 in the radial direction and the
number of the through holes 22 on the other side is less than the
number of the through holes 22 on the one side.
Fourth Embodiment
[0039] A fourth embodiment is another case that a magnetic
unbalance part 24 is provided by boring a through hole 22 on a
circumferential wall of a core guide part 19. In the example of the
above-described third embodiment, the several through holes 22 are
provided only for the one side of the core guide part 19, which is
opposed to the other side in the radial direction of the core guide
part 19. However, as shown in FIGS. 7A and 7B, in the fourth
embodiment, the magnetic unbalance part 24 is provided by providing
the same number of the through holes 22 both on one side (left side
in FIG. 7A) and the other side of a magnetic saturation part 21,
which are opposed each other in a radial direction of the core
guide part 19, and by changing diameters of the through holes 22.
In the example as shown in FIGS. 7A and 7B, the diameters of the
through holes 22 are larger on the one side than on the other side
of the magnetic saturation part 21 in the radial direction.
Accordingly, magnetic resistance is larger on the one side than on
the other side of the magnetic saturation part 21 in the radial
direction. Therefore, when a movable core 16 moves in the guide
hole 19a in an axial direction of the core guide part 19, the
movable core 16 is attracted to and contacts with the one side of
the core guide part 19 in the radial direction, where a magnetic
force more strongly acts on the movable core 16, and rotation of
the movable core 16 is prevented.
Fifth Embodiment
[0040] A fifth embodiment is a case that a coating agent 23 is
applied to an outer circumferential surface of a movable core 16,
which is attracted to and contacts with one side of a core guide
part 19 in a radial direction of a core guide part 19 when the
movable core 16 is attracted to a fixed core 20 and moves in a
guide hole 19a in an axial direction of the core guide part 19. In
the first to fourth embodiments, because the magnetic resistance is
larger on the one side than on the other side of the core guide
part 19 in the radial direction, the movable core 16 is attracted
to and contacts with the one side of the core guide part 19.
Accordingly, rotation of the movable core 16 is prevented. In this
case, when the movable core 16 moves in the guide hole 19a, the
outer circumferential surface of the movable core 16 which slides
on an inner circumferential surface of the guide hole 19a, i.e., a
sliding surface of the movable core 16 is areally almost fixed. In
other words, the sliding surface is within an almost fixed range in
a circumferential direction of the movable core 16. Thus, as shown
in FIG. 8, it is enough to apply the coating agent 23 only for the
sliding surface of the movable core 16, which is attracted to and
contacts with the core guide part 19, and the coating agent 23 need
not be applied to the entire outer circumferential surface of the
movable core 16. Therefore, a consumption amount of the coating
agent 23 can be reduced.
[0041] Modifications of the above embodiments will be described. In
the first embodiment, the electromagnetic valve of the invention is
applied to the purge valve 7 utilized in the fuel vapor treatment
system of the vehicle. However, the electromagnetic valve can be
applied to the canister control valve 10. The electromagnetic valve
of the invention can be applied also to, for example, an hydraulic
control valve utilized in a valve timing control device of an
internal combustion engine, or an hydraulic solenoid utilized in an
automatic gear shifting device of an vehicle.
[0042] To sum up, the electromagnetic valve of the above
embodiments may be described as follows.
[0043] The electromagnetic valve includes the valve seat 13, the
valving element 11, and the solenoid part 12. The valve seat 13 has
the annular shape and defines the valve hole 14 that opens radially
inward of the valve seat 13. The valving element 11 is movable
between the valve-closing position where the valving element 11 is
engaged with the valve seat 13 to close the valve hole 14 and the
valve-opening position where the valving element 11 is disengaged
from the valve seat 13 to open the valve hole 14. The solenoid part
12 drives the valving element 11 by utilizing magnetic force of the
electromagnet. The solenoid part 12 includes the coil 15, the core
guide part 19, the fixed core 20, and the movable core 16. The coil
15 becomes the electromagnet upon energization thereof. The core
guide part 19 has the cylindrical shape and is arranged radially
inward of the coil 15 to form the magnetic circuit. The fixed core
20 is arranged on one end side of the core guide part 19 in the
axial direction of the core guide part 19 and is magnetized by the
electromagnet. The movable core 16 is accommodated inside the core
guide part 19 to be opposed to the fixed core 20 in the axial
direction and is reciprocated inside the core guide part 19 in
accordance with whether the electromagnet is turned on or off. The
valving element 11 moves integrally with the movable core 16 to
open or close the valve hole 14. The core guide part 19 includes
the magnetic unbalance part 24 where the magnetic force applied
between the core guide part 19 and the movable core 16 is different
between on one side and the other side of the core guide part 19,
which are opposed to each other in the radial direction of the core
guide part 19.
[0044] In the electromagnetic valve of the invention, the magnetic
unbalance part 24 is provided in the core guide part 19, which has
the cylindrical shape and is a part of the magnetic circuit located
radially inward of the coil 15. More specifically, the magnetic
force applied between the movable core 16 and the core guide part
19 is different between on the one side and the other side of the
core guide part 19, which are opposed to each other in the radial
direction of the core guide part 19. Thus, when the movable core 16
is attracted to the fixed core 20 by the action of the
electromagnet, i.e., when the movable core 16 moves inside the
guide hole 19a in the axial direction of the core guide part 19,
the movable core 16 is attracted to and contacts with one side of
the core guide 19 in the radial direction of the core guide part 19
(the one side or the other side of the core guide part 19 in the
radial direction of the core guide part 19) where the magnetic
force more strongly acts on the movable core 16. Hence, rotation of
the movable core 16 may be prevented, and accordingly, the valving
element 11 moving integrally with the movable core 16 may be always
engaged with the same position of the valve seat 13 at closing time
when the valve hole 14 is closed. Therefore, the valving element 11
and the valve seat 13 may be shaped to conform to each other, and
thereby, the sealing performance at the closing time can be
improved. Additionally, the movable core 16 is attracted to and
contacts with one side of the core guide part 19 in the radial
direction when the movable core 16 moves inside the core guide part
19. Thus, sliding resistance is produced between the movable core
16 and the core guide part 19. As a result, the travel speed of the
movable core 16 becomes slow, and therefore, an impact noise, which
is produced when the movable core 16 contacts with the fixed core
20, can be reduced.
[0045] The core guide part 19 may include the magnetic saturation
part 21 along the entire outer circumference thereof. The magnetic
saturation part 21 includes the recessed part on the outer
peripheral surface thereof, to reduce the thickness of the core
guide part 19, thereby decreasing the magnetic-path cross-sectional
area of the magnetic saturation part 21. At the magnetic unbalance
part 24, the magnetic-path cross-sectional area of the magnetic
saturation part 21 is different between on the one side and the
other side of the core guide part 19. In the above-described
structure, as the magnetic-path cross-sectional area of the
magnetic saturation part 21 is smaller, the magnetic resistance of
the core guide part 19, which is the part of the magnetic circuit,
may become larger. Thus, the magnetic force applied between the
core guide part 19 and the movable core 16 may increase. If a
magnetic-path cross-sectional area of one side of the core guide
part 19, which is opposed to the other side of the core guide part
19, is made smaller than a magnetic-path cross-sectional area of
the other side of the core guide part 19, the magnetic force
applied between the core guide part 19 and the movable core 16 may
act larger on the one side than on the other side of the core guide
part 19. Therefore, the movable core 16 can be attracted to the one
side of the core guide part 19.
[0046] The outer diameter center Ob of the magnetic saturation part
21 may be positioned eccentrically with respect to the diameter
center Oa of the core guide part 19. When the outer diameter center
Ob of the magnetic saturation part 21 coincides with the diameter
center Oa, a magnetic-path cross-sectional area of the magnetic
saturation part 21 is a constant in the circumferential direction
of the core guide part 19. However, if the magnetic saturation part
21 is provided such that the outer diameter center Ob of the
magnetic saturation part 21 is eccentrically positioned relative to
the diameter center Oa of the core guide part 19, the magnetic
unbalance part 24 can be provided, where the magnetic-path
cross-sectional area of the magnetic saturation part 21 is
different between the one side and the other side of the core guide
part 19, which are opposed to each other.
[0047] The outer diameter center Ob of the magnetic saturation part
21 may coincide with the outer diameter center Oa of the core guide
part 19. Additionally, the diameter center Oc of the inner
peripheral surface of the core guide part 19, which accommodates
the movable core 16, may be located eccentrically with respect to
the outer diameter center Oa of the core guide part 19.
Specifically, the inner peripheral surface of the core guide part
19 may be shifted to either one side in the radial direction of the
core guide part 19 relative to the outer peripheral surface of the
core guide part 19 (on the one side or the other side of the core
guide part 19). Accordingly, the magnetic unbalance part 24 can be
provided, where the magnetic-path cross-sectional area of the
magnetic saturation part 21 is different between the one side and
the other side of the core guide part 19, which are opposed to each
other.
[0048] At the magnetic unbalance part 24, the core guide part 19
may include the through hole 22, which passes through the
circumferential wall of the core guide part 19, only on the one
side or the other side of the core guide part 19. In the
above-described structure, because magnetic resistance increases,
the magnetic force between the movable core 16 and the core guide
part 19 may increase. For example, if the through hole 22 is
provided only on one side of the core guide part 19, magnetic
resistance of the one side becomes larger than that of the other
side of the core guide part 19. Accordingly, the movable core 16
can be attracted to the one side of the core guide part 19, in
which the magnetic force applied between the movable core 16 and
the core guide part 19 is relatively strong.
[0049] At the magnetic unbalance part 24, each of the one side and
the other side of the core guide part 19 may include at least one
through hole 22, which passes through the circumferential wall of
the core guide part 19. Moreover, the number of the through holes
22 on the one side of the core guide part 19 may be different from
the number of the through holes 22 on the other side of the core
guide part 19. In this instance, the numbers of the through holes
22 passing through the circumferential wall of the core guide part
19 on the one side and on the other side of the core guide part 19
are different from each other. Hence, a magnitude of the magnetic
resistance is different between the one side and the other side of
the core guide part 19. For example, when the number of the through
holes 22 on the one side of the core guide part 19 is larger than
the number of the through holes 22 on the other side of the core
guide part 19 (here, all the hole diameters of the through holes 22
are of the same size), the one side is larger than the other side
in the magnitude of the magnetic resistance. Therefore, the movable
core 16 can be attracted to the one side of the core guide part 19,
where the magnetic force more strongly acts between the movable
core 16 and the core guide part 19.
[0050] At the magnetic unbalance part 24, each of the one side and
the other side of the core guide part 19 may include a through hole
22, which passes through the circumferential wall of the core guide
part 19. Additionally, a diameter of the through hole 22 on the one
side of the core guide part 19 and a diameter of the through hole
22 on the other side of the core guide part 19 may be different
from each other. In this case, the diameters of the through holes
22 passing through the circumferential wall of the core guide part
19 on the one side and the other side of the core guide part 19,
which are opposed to each other, are different from each other.
Thus, a magnitude of the magnetic resistance is different between
the one side and the other side of the core guide part 19. For
example, when the diameter of the through holes 22 on the one side
of the core guide core 19 is larger than the diameter of the
through holes 22 on the other side of the core guide core 19, the
one side is larger than the other side in the magnitude of the
magnetic resistance. Therefore, the movable core 16 can be
attracted to the one side of the core guide part 19, where the
magnetic force more strongly acts between the movable core 16 and
the core guide part 19.
[0051] The core guide part 19 may include the magnetic saturation
part 21 along an entire outer circumference thereof, and the
magnetic saturation part 21 includes the recessed part on an outer
peripheral surface thereof, to reduce the thickness of the core
guide part 19, thereby decreasing the magnetic-path cross-sectional
area of the magnetic saturation part 21. Furthermore, the through
hole 22 on the one side of the core guide part 19 and the through
hole 22 on the other side of the core guide part 19 are provided at
the magnetic saturation part 21. By forming the magnetic saturation
part 21 in the core guide part 19, a magnetic flux flowing directly
from the core guide part 19 to the fixed core 20 decreases. Hence,
the magnetic force applied between the core guide part 19 and the
movable core 16 increases by the decrease of the magnetic flux.
Therefore, an magnetic attraction force acting between the core
guide part 19 and the movable core 16 increases. If the magnetic
unbalance part 24 is provided by boring the through holes 22 at the
magnetic saturation part 21, the movable core 16 can be attracted
to one side (either side of the one side or the other side of the
core guide part 19 in its radial direction) of the core guide part
19 on which the magnetic force strongly affects to the movable core
16.
[0052] Only a part of the outer peripheral surface of the movable
core 16, which slides on the inner peripheral surface of the core
guide part 19, may be coated with the coating agent 23. In the
electromagnetic valve of the invention, when the movable core 16 is
attracted to the fixed core 20 and moves inside the core guide part
19 due to the action of the electromagnet, the movable core 16 is
attracted to and contacts with one side of the core guide part 19
(either side of one side or the other side of the core guide part
19 in the radial direction), the movable core 16 thereby being
prevented from rotating. In this case, the outer circumferential
surface of the movable core 16 which slides on the inner
circumferential surface of the core guide part 19, i.e., the
sliding surface of the movable core 16 is areally almost fixed. In
other words, the sliding surface is within an almost fixed range in
a circumferential direction of the movable core 16. Thus, the
coating agent 23 need not be applied to the entire outer
circumferential surface of the movable core 16, and it is enough to
apply the coating agent 23 only for the sliding surface of the
movable core 16. Therefore, the consumption amount of the coating
agent 23 can be reduced.
[0053] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *